Transformer design is often the art of compromising the conflicting requirements of electrical performance, space requirements and manufacturing and fabrication costs. The electrical performance requirements of the windings often conflict with the difficulties of winding the desired coils with the proper geometry and mechanical integrity at a reasonable cost. At the very least, a transformer winding must have the required number of turns, adequate current handling capacity and the necessary structural strength to withstand electrically induced mechanical stresses. Additional considerations include securing good coupling between the windings and maximizing utilization of the core windows. Many times the practical difficulties inherent in winding the transformer coils such as getting the coil to lay properly, getting proper tension, positioning in and filling the core windows require compromises that limit ultimate electrical performance.
A suitable technique for improving electrical performance while minimizing the aforementioned difficulties has been to use a preformed winding having a channel cross section into which another prewound winding is mechanically inserted. This solves many of the above mentioned constructional difficulties without compromising electrical performance. It also advantageously permits a low profile transformer design suitable for card-type circuit packs. Such an arrangement is disclosed in the pending patent application of F. T. Dickens and W. A. Peterson, entitled "Low Profile Magnetic Structure In Which One Winding Acts As Support For A Second Winding", filed Aug. 13, 1984, Ser. No. 639,859 now U.S. Pat. No. 4,583,068. The arrangement disclosed therein comprises a transformer having a one turn preformed secondary winding and further having the primary enclosed within a channel cross section of the secondary winding. This arrangement, however, is limited to situations where a sing1e turn winding is appropriate since no arrangement exists permitting the preformed winding to have multiple turns.